Updated the glossary description for the B variable. There
was some confusing "source directory" terminology in there.
(From yocto-docs rev: 72fbf86ca9612a0dca741f08315efed1d9efa0b1)
Signed-off-by: Scott Rifenbark <scott.m.rifenbark@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>